為了定義開放測試場（Open Area Test Site, OATS）的品質，IEC的CISPR和美國的ANSI，進一步規定了有關開放測試場品質方面的量化評估方法，係運用場地衰減之模型來驗證，ANSI為了消除因使用不同天線，所造成場衰減量的不正確，而採行了正規化場衰減量（Normalized Site Attenuation, NSA）的觀念。為了嚴格要求開放測試場的品質，實測的NSA值和理論值相比較，在所有的頻段上，兩者的差異幅度必須在(+/-)4 dB之內，則此開放測試場可稱為一標準的測試場。
目前全世界皆利用NSA理論值做為開放測試場的檢驗標準，然而其理論根據在某些假設和簡化條件下，衍生出的非理想因子，極有可能對實際NSA的量測造成誤差，進而影響場地驗證結果。為求瞭解這些非理想因子影響的機制和程度，本文針對NSA的理論加以研究，找出這些非理想因子，利用動差數值方法(MoM)進行模擬、分析和比較。文章中討論NSA量測時，接收端阻抗不匹配的情況下，量測結果有近6 dB的差異。同時也說明非完美導體接地面之導電係數的大小與NSA理想值的關係，可歸納出任何金屬材質之接地面可視為完美導體，而導電係數在1000 S/m以下者，將使NSA值上升。此外，本文特別針對台灣潮濕多雨的氣候條件，模擬得出雨後時，接地面上覆蓋一層水面後，會使NSA值降低。至於在3米近距離量測時，天線為水平極化的情況下，近場效應會在低頻段產生2 dB左右的誤差。最後，考量置入一非導電材質之量測桌子於測試場中，發現相對介電係數以及導電係數較大者，對NSA值的影響也較大，就木質材質而言，其差異性可達到3 dB左右。
經由本文的研究結果，可清楚瞭解各非理想因子的影響模式，其有關差異性的比較，可提供日後在NSA量測上，進行誤差修正的參考。

The CISPR of IEC in European and the ANSI in American use the model of site attenuation to evaluate and quantify the quality of OATS. The ANSI also uses the concept of Normalized Site Attenuation (NSA) to eliminate the effects brought about by different antennas, which may cause the inaccuracy of site attenuation. To stringently require the quality of OATS, the measured values of NSA have to be compared with the theoretical ones. If their differences are within (+/-)4 dB at all frequencies, the test environment of the OATS can be accepted.
At present, the theoretical values of NSA are used as a standard for verifying the OATS in the world. However, many non-ideal factors derived from certain assumptions and simplifications of the NSA may cause the measured NSA to deviate from the theoretical values. To understand the manner and extent of the effects, in this thesis we find out the non-ideal factors by studying the NSA by numerically simulating the effects of each factor on NSA measurement by the method of moment (MoM), and the results are analyzed and discussed. We find that there is a difference of 6 dB on the NSA when the impedance of the receive antenna is mismatched. Meanwhile, we also study the relationship between the conductivity of non-perfect electrical conductor and the ideal value of NSA. We conclude that a ground plane made by metal can be regarded as a PEC one. However, the values of NSA will increase if the conductivity of ground plane is below 1000 S/m. Besides, considering the humid Taiwan climate in particular, we investigate the condition of a thin layer of water covering the ground plane after rain and the results show that the effect of the water plane will decrease the values of NSA. As for the measurement at a distance of 3 m, a deviation of 2 dB at low frequencies arises from the effect of near field for the case of horizontal polarization. Finally as for the non-conducting table in OATS, our results show that the larger values of relative permittivity and conductivity of table result in the larger change of NSA value. The difference can be 3 dB for the case with a wooden table.
With results of our research, the effects of non-ideal factors on NSA measurement can be comprehended clearly. The comparison of the differences also can be used as a reference for the modification of the NSA measurement in the future.

致謝 I
摘要 III
摘要（英文） IV
目錄 VI
圖表目錄 VIII

第一章 介紹 1
1.1 研究背景 1
1.2 研究目的 3

第二章 正規化場衰減量理論值計算與量測 6
2.1 正規化場衰減量理論值 6
2.1.1 自由空間中遠場電場表示式 6
2.1.2 水平極化半波長天線的輻射電場 9
2.1.3 鉛直極化半波長天線的輻射電場 12
2.1.4 NSA值的表示式 13
2.2 正規化場衰減量的量測程序 15

第三章 模擬環境的建立 17
3.1 天線因子（Antenna Factor, AF） 17
3.2 水平極化半波長天線之測試場模型 18
3.3 鉛直極化半波長天線之測試場模型 19
3.4 阻抗匹配造成的差異性 21

第四章 接地面材質之模擬結果與分析 23
4.1 金屬接地面 23
4.2 低導電材質接地面 23
4.3 接地面導電係數之結論 24

第五章 台灣多雨潮濕的氣候對量測環境的影響 27
5.1 理論分析 27
5.1.1 水平極化 27
5.1.2 鉛直極化 33
5.2 模擬環境 36
5.3 模擬結果 37
5.3.1 水平極化 37
5.3.2 鉛直極化 42
5.4 水面效應的結論 42
5.5 近場效應的影響 47
5.5.1 場衰減量的近場修正 47
5.5.2 考慮水面覆蓋金屬接地面之場衰減近場的修正 49
5.5.3 水平極化之近場影響程度 49
5.5.4 鉛直極化之近場影響程度 50
5.6 近場水面效應的結論 57

第六章 置放待測物的量測桌面對量測環境的影響 58
6.1 接收端電場強度的變化 58
6.2 模擬環境 59
6.3 模擬結果 63
6.3.1 水平極化 63
6.3.2 鉛直極化 63
6.4 結論 66

第七章 結論 70

參考文獻 72

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